The invention relates to a semiconductor device and a method for fabricating the same, and more particularly to a semiconductor device having a modified recess channel gate and a method for fabricating the same.
As the design rule of semiconductor devices becomes finer, the gate channel length becomes smaller. Accordingly, in semiconductor devices having gate channel lengths of 70 nm or less, it is difficult to set a critical voltage with a planar channel structure. Thus, semiconductor devices having various recess channel gates have been proposed to efficiently and substantially increase the effective channel length.
Referring to FIG. 1, a device isolation region 110 is disposed on a semiconductor substrate 100 (see FIG. 2) to define an active region 101. A gate line 121 is disposed in the direction across the active region 101. The gate line 121 may be understood as a recess channel gate for increasing the effective channel length.
FIG. 2 illustrates a major axis cross section taken along a line A-A′ in FIG. 1 and FIG. 3 illustrates a minor axis cross section taken along a line B-B′ in FIG. 1.
Referring to FIG. 2, a recess channel trench 120 is formed by etching the active region 101 of the semiconductor substrate 100. When the recess channel trench 120 is formed, a major axis length 102 of the active region becomes longer and the effective channel length increases. On the other hand, referring to FIG. 3, a minor axis length 103 of the active region does not change even after the recess channel trench 120 is formed, so that there is no increase in the effective channel width.
As mentioned above, a semiconductor device having a recess channel gate has an increased effective channel length. However it is difficult to increase the effective channel width.